(6) are in fact described by the Bayesian network shown in Fig.1.
In the Bayesian network below, and are evidence frames and is the conclusion frame.
A Bayesian network is a kind of graph which is used to model events that cannot be observed.
Bayesian networks are mainly used in the field of (unassisted) machine learning.
Such conditional independence relations can be represented with a Bayesian network.
Then the situation can be modeled with a Bayesian network (shown).
There are several equivalent definitions of a Bayesian network.
The term hierarchical model is sometimes considered a particular type of Bayesian network, but has no formal definition.
In general, however, any moderately complex Bayesian network is usually termed "hierarchical".
The paper is about both parameter and structure learning in Bayesian networks.